> Are they not using venvs or something? It should be as simple as python -m venv venv; ./activate; pip install -r requirements.txt

In most cases, it would be possible to do close to that, but it is extremely common to run into things being distributed in the AI/ML space with install instructions that don’t include that, and instruct you to have a global install of a certain Python version, and then to pip install the dependencies (and globally install non-Python package dependencies, if there are any), so even if they’d work in a venv, you have to (1) indepently know you should be doing that, and (b) translate the instructions – which where (1) applies is usually trivial if all the dependencies are proper python packages, but can be more involved otherwise.

So, yeah, I can see that a lot of the time the path of least resistance is just to create an isolated container environment for it.